PROJECT SUMMARY/ABSTRACT Epilepsy is a highly prevalent disorder affecting 1% of the world?s population but our understanding of the molecular mechanisms that underlie epilepsy is still incomplete. Deficiency in the function of GABA reuptake mediated by GABA transporter type 1 (GAT1), has been implicated in absence epilepsy and heterozygous mutations in the gene SLC6A1 which encode GAT1 cause myoclonic astatic epilepsy, a generalized seizure disorder with onset in infancy. Several questions remain regarding the pathophysiology of GAT1 hypofunction, including whether the disease can be modeled in zebrafish as it can in rodents and whether the disorder is related to primary constitutive versus secondary developmental consequences of GAT1 hypofunction. Therapeutically, a major question is whether it is possible to identify disease-specific treatments for GABA reuptake deficiency. These questions represent major gaps in knowledge whose answers could inform the timing and nature of treatment for patients with MAE and other generalized epilepsy syndromes involving GAT1 hypofunction. ?The current proposal will close these gaps by establishing a novel zebrafish model of GAT1 hypofunction to address questions related to the pathogenesis of the disorder and by testing whether a novel in vitro fluorescence-mediated cell-based assay of GAT1 function can be used to identify positive modulators with therapeutic value.?The proposed research will provide essential insights into the mechanisms of a generalized epilepsy syndrome related to slc6a1/GAT1 hypofunction and establish platforms for future drug screening and in vivo testing to reverse the pathophysiology of the disorder. The proposal under consideration combines an innovative research project with translational implications, excellent mentorship in science and career development, and extensive institutional resources at Boston Children?s Hospital, Massachusetts General Hospital, and Harvard Medical School, which should facilitate the transition into an independent physician-scientist by the end of the award period. In sum, the proposal provides a framework for a robust independent research program balancing mechanistic and translational investigations of epilepsy. It is well-integrated with the research and clinical interests of the applicant, whose career goal is to become an independent physician scientist with a focus on high-throughput biology and drug screening to understand the mechanisms of epilepsy and to identify corresponding treatments.